This question should be appended to the other question you asked about cloud computing. What I mean by that is if the cloud computing revolution comes about, the number of IT jobs will decrease greatly. Often times as technologies advance, people of all walks of life lose jobs. The automation of industries are good examples.
That and outsourcing can also have a larger impact. As systems become easier to remotely manage, an outsourced group can manage them for more than one company and those companies would then lay off their own IT as a result. It really depends on the organization and what your function there is and will be as things change. Some companies prefer to keep everything in house and by doing so will be less likely to lay anyone off, at least not in large numbers.
I would have to say that yes the total number of IT jobs will go down in the next year. A sad fact of the current economy in the US companies will be cutting corners, and slimming things own so that they can stay competitive and keep there stock holders happy. This unfortunately means layoffs in all business sectors including IT.
You could look at it though as a net change of zero. Companies may be cutting back on things like outsourcing and pull some services inside which would create the need for IT staff to deal with those activities, or companies might release people and do more outsourcing which would create more of a need in that line of IT jobs. I do think there might be some reduction in the short term as a reaction to economic conditions but in the long term IT will continue to be a growing workforce… maybe not as much as healthcare, but likely close to it.